This research project is designed to further our understanding of the photo- and biochemistry of visual pigments. Its ultimate aim is to elucidate how these substances function within the photoreceptor and how their integrity, synthesis and regeneration depend on the reciprocal exchange of metabolites, membrane material and precursors between pigment epithelium and retina. A major emphasis in this work concerns the metabolism, interconversion, storage and transport of vitamin A isomers and congeners in ocular tissues. The effects of hormones, environmental light, metamorphosis, light- and dark-adaptation will be investigated. The possibility that an enzyme that interconverts retinol and 3-dehydroretinol is genetically determind will be explored. Also included in the present project is the determination of retinal configuration in visual pigment photoproducts, the degradation of rhodopsin in shed fragments of rod outer segments, and the binding of lectins to the plasma membranes of rods, cones and pigment epithelium cells.